What are the limitations of correlational research?

A41-year-old man comes to the clinic complaining of a chronic cough over the past 4 months, which has now been accompanied by haemoptysis. he denies smoking or any past medical history. on physical examination, his head and neck examination is normal. his lungs have diffuse bilateral rales. cardiac examination is normal. laboratory findings reveal na 142 meq/l, k 4.2 meq/l, cl 110 meq/l, hco3 24 meq/l, bun (blood urea nitrogen) 39 mg/dl, creatinine 2.9 mg/dl. urinalysis reveals microscopic haematuria and 4+ proteinuria. which of the following serologic blood tests would most confirm the suspected diagnosis? - anti-glomerular basement membrane antibodies- anti-mitochondrial antibodies- anti-neutrophilic antibodies- anti-parietal cell antibodies- anti-smooth muscle antibodies